The background of the invention will be set forth in two parts.
1. Field of the Invention
This invention relates to folding support structures and more particularly to those structures used as child strollers and chairs.
2. Description of the Prior Art
Folding structures of the type adapted to support an object or a person are well known. By far, most of these structures fold only in one dimension, that is, they fold "flat." This is a rather bulky configuration and leaves something to be desired when considering ease of storage and transportation.
For some applications, ground wheels have been provided in order to facilitate movement of the structure when it is supporting a person, for example. A typical application of this type is a folding wheel chair. Again, most of these chairs fold only in one dimension, i.e., laterally.
In more recent times, much interest has been directed to folding baby carriages or strollers having wheels for ease of movement of the stroller and its occupant. A very popular example of this type structure is called a "stick folding" or "umbrella" structure since it folds in two dimensions to provide an elongated thin silhouette. A typical example of this type configuration is described in U.S. Pat. No. 3,390,893 directed to structures for folding baby carriages, chairs, and the like.
Prior art structures may include two X frames which are directly interpivotally connected by means of two-axes pivot joints, the frames being held in their unfolded position at a fixed angle with respect to each other by rigid brace members pivotally connected to the frames. One of the X frames is usually more or less vertical and located at the back of the stroller, while the other is at the bottom of the structure and is generally horizontal in its unfolded position. In its folded configuration, the two X frames collapse and all elongated elements thereof are nearly parallel. The brace elements also fold about pivoted interconnections so that the ends of the X frames come together. This moves the front wheels near the location of the carriage's handles where they may soil clothes, for example, and, because of this elevated mass, a clip is required in order to retain the structure in a folded position. Thus, it should be evident that a foldable support structure that is simple in construction and that folds into a slim, trundable configuration while maintaining a low center of mass with all wheels always located near the ground level and that does not require a clip mechanism to hold the structure in its folded position would constitute a significant advancement of the art.